Both transparent and opaque plastic films are used as wrapping and/or packaging materials in substantially every area of manufacturing and marketing of modern commerce. The plastic packaging materials include rigid materials which provide protection from outside impact or crushing forces, including the somewhat flexible but brittle packaging materials which provide a form fit around the product. This type of plastic packaging material may typically be heated so that it shrinks around the product. In addition, extremely pliable plastic films are used which do not always protect the product from outside crushing or impact forces, but do provide excellent protection against undesirable environment, such as moisture, dirt, sand, corrosive air or gases, etc.. The present invention is primarily concerned with such pliable plastic materials.
More particularly, the present invention is concerned with drawing the pliable packaging material taut around the product prior to sealing the open end of the package. Drawing the material taut helps eliminate use of excessive material, and also helps maintain the integrity and shape of the product so as to allow easier storage, stacking and display of the product. However, in addition to drawing the packaging taut around the product, the apparatus must also avoid crushing or distorting the shape of the product during the sealing process by drawing the packaging material too taut.
Therefore, it is an object of this invention to provide methods and apparatus for drawing a pliable plastic wrapping material taut around a product (including fragile products) prior to sealing the package, and without injury to the product.
There are, of course, various techniques for closing or sealing pliable plastic materials around a product. For example, a loaf of bread may be placed in a pliable plastic bag, the open end gathered together and then a wire-tie or plastic clip placed around the gathered material to close the package. Although it is understood that the Kwik-Lok company has used large, five (5) inch diameter brushes to help gather the material of a plastic bag for closing the package with a wire-tie or plastic clip, it is clear that the use of such brushes could not accomplish the intent of the present invention. U.S. Pat. Nos. marked on KWIK LOK equipment, but not available to the applicant at the time of filing include: 3,526,337; 3,519,196; 3,481,461; 3,446,344; 3,439,867; 3,417,912; 3,417,864; 3,417,863; 3,412,895; 3,381,442; 3,370,396; 3,270,874; 3,270,873; 3,270,872; 3,270,481; 3,190,053; 3,164,250; 3,164,249; 3,163,972; 3,163,970; 3,163,969; 3,067,534; 3,061,983; 2,907,586; and 2,705,100. The use of wire-ties or plastic clips to close plastic bags have been used to a much lesser extent for protecting and enclosing articles of clothing, linens, other cloth items and the like. However, to better display the product, to protect the product from wrinkles while in the package, and to maintain the shape of the packaged product to facilitate stacking and storage, it has been found that packaging material should closely conform to the shape of the product, and the packaging material sealed around the perimeter or edge of the product (such as by heat) with a minimum amount of excess material. Therefore, it is another object of this invention to draw the packaging material taut around the product so that the packaging can be sealed proximate the edge of the product.
To assure the minimum use of packaging material, and to ensure a more attractive product, it is desirable that the sealed packaging material include a minimum of folds and/or wrinkles at the seal. Therefore, it is yet another object of this invention to provide means for smoothing away wrinkles and folds in the packaging material prior to sealing.